Why do cameras use a single exposure rather than integrating across many very quick reads?@whatsisname: sorry, I don't understand your point. The noise is a random process with a certain rate depending on the ISO and other parameters. The rate of noise should be the same for short or long exposure. Maybe this is not completely true because it depends on the temperature and so for long exposure you could have more noise rate. By the way, supposing constant noise rate you should obtaing more noise for longer exposure.

Jan23

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Why do cameras use a single exposure rather than integrating across many very quick reads?I think File size is not a big issue, in my mind you can choose to shoot in integral mode or in differential mode. Timelapse need a lot of memory, this doesn't mean people are not doing it. For the Exposure I think you are wrong as mattdm said and I think the noise is the same in the case you do only one shoot or summing more shoots, the only difference is that you open and close your shutter. When summing different frames you are summing the signal and the noise. I think the proof is that the sum of two independent Poissonian random variable is a still Poissonian distributed.